﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;

namespace SharpCommon.ORM.Common
{
    public delegate object GetHandler(object source);
    public delegate void SetHandler(object source, object value);
    public delegate object InstantiateObjectHandler();
    public sealed class DynamicMethodCompiler
    {
        private DynamicMethodCompiler() { }
        internal static InstantiateObjectHandler CreateInstantiateObjectHandler(Type type)
        {
            ConstructorInfo constructorInfo =type.GetConstructor(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance, null, new Type[0], null);
            if (constructorInfo == null)
            {
                throw new ApplicationException(string.Format("The type {0} mustdeclare an empty constructor (the constructor may be private, internal, protected,protected internal, or public).", type));
            }
            DynamicMethod dynamicMethod = new DynamicMethod("InstantiateObject",MethodAttributes.Static |MethodAttributes.Public, CallingConventions.Standard,typeof(object),null, type, true);
            ILGenerator generator = dynamicMethod.GetILGenerator();
            generator.Emit(OpCodes.Newobj, constructorInfo);
            generator.Emit(OpCodes.Ret);
            return (InstantiateObjectHandler)dynamicMethod.CreateDelegate
            (typeof(InstantiateObjectHandler));
        }
        internal static GetHandler CreateGetHandler(Type type, PropertyInfo propertyInfo)
        {
            MethodInfo getMethodInfo = propertyInfo.GetGetMethod(true);
            DynamicMethod dynamicGet = CreateGetDynamicMethod(type);
            ILGenerator getGenerator = dynamicGet.GetILGenerator();
            getGenerator.Emit(OpCodes.Ldarg_0);
            getGenerator.Emit(OpCodes.Call, getMethodInfo);
            BoxIfNeeded(getMethodInfo.ReturnType, getGenerator);
            getGenerator.Emit(OpCodes.Ret);
            return (GetHandler)dynamicGet.CreateDelegate(typeof(GetHandler));
        }
        internal static GetHandler CreateGetHandler(Type type, FieldInfo fieldInfo)
        {
            DynamicMethod dynamicGet = CreateGetDynamicMethod(type);
            ILGenerator getGenerator = dynamicGet.GetILGenerator();
            getGenerator.Emit(OpCodes.Ldarg_0);
            getGenerator.Emit(OpCodes.Ldfld, fieldInfo);
            BoxIfNeeded(fieldInfo.FieldType, getGenerator);
            getGenerator.Emit(OpCodes.Ret);
            return (GetHandler)dynamicGet.CreateDelegate(typeof(GetHandler));
        }
        internal static SetHandler CreateSetHandler(Type type, PropertyInfo propertyInfo)
        {
            MethodInfo setMethodInfo = propertyInfo.GetSetMethod(true);
            DynamicMethod dynamicSet = CreateSetDynamicMethod(type);
            ILGenerator setGenerator = dynamicSet.GetILGenerator();
            setGenerator.Emit(OpCodes.Ldarg_0);
            setGenerator.Emit(OpCodes.Ldarg_1);
            UnboxIfNeeded(setMethodInfo.GetParameters()[0].ParameterType,
            setGenerator);
            setGenerator.Emit(OpCodes.Call, setMethodInfo);
            setGenerator.Emit(OpCodes.Ret);
            return (SetHandler)dynamicSet.CreateDelegate(typeof(SetHandler));
        }
        internal static SetHandler CreateSetHandler(Type type, FieldInfo fieldInfo)
        {
            DynamicMethod dynamicSet = CreateSetDynamicMethod(type);
            ILGenerator setGenerator = dynamicSet.GetILGenerator();
            setGenerator.Emit(OpCodes.Ldarg_0);
            setGenerator.Emit(OpCodes.Ldarg_1);
            UnboxIfNeeded(fieldInfo.FieldType, setGenerator);
            setGenerator.Emit(OpCodes.Stfld, fieldInfo);
            setGenerator.Emit(OpCodes.Ret);
            return (SetHandler)dynamicSet.CreateDelegate(typeof(SetHandler));
        }
        private static DynamicMethod CreateGetDynamicMethod(Type type)
        {
            return new DynamicMethod("DynamicGet", typeof(object),
            new Type[] { typeof(object) }, type, true);
        }
        private static DynamicMethod CreateSetDynamicMethod(Type type)
        {
            return new DynamicMethod("DynamicSet", typeof(void),
            new Type[] { typeof(object), typeof(object) }, type, true);
        }
        private static void BoxIfNeeded(Type type, ILGenerator generator)
        {
            if (type.IsValueType)
            {
                generator.Emit(OpCodes.Box, type);
            }
        }
        private static void UnboxIfNeeded(Type type, ILGenerator generator)
        {
            if (type.IsValueType)
            {
                generator.Emit(OpCodes.Unbox_Any, type);
            }
        }
    }
}
